4.8 Emacs Related Commands

C-\

Begin Meta command in Vi or Insert states. Most often used as C-\ x (M-x).

Note: Emacs binds C-\ to a function that offers to change the
keyboard input method in the multilingual environment. Viper overrides this
binding. However, it is still possible to switch the input method by typing
\ C-\ in the Vi command state and C-z \ C-\ in the Insert state.
Or you can use the MULE menu on the menubar.

C-z

In Insert and Replace states, prepare Viper to accept the next command and
execute it as if Viper was in Vi state. Then return to Insert state.